A physico-chemical basis for novel cementitious binders

The drive towards sustainability in construction is shaping our attitudes towards alternatives to Portland cement. Although the cement and concrete industry is essentially sustainable with respect to raw materials supply, and concrete manufacture actually gives relatively low CO2 emissions per unit volume compared to most competitive construction materials, the current focus on climate change has led to concerns about cement industry-generated CO2. Thus, there is interest in developing alternative cements with lower associated CO2 emissions. This paper seeks to provide a context for innovative development through a review of what is meant by a hydraulic cementitious binder, identification of key physico-chemical properties of successful binders and how novel systems generally rely on similar factors. Concepts such as reactivity, availability of reactive species and physico-chemical drivers for the formation of cementitious systems are discussed as a basis for introducing and reviewing recent developments in the search for ever more environmentally sustainable cements.